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,10 all whom t'tmay concern.-

Be it known that I,.,JOHN T. AVERILL, of StLPaul, Ramsey.county,,Minnesota,haveinvented anew and useful process by means UN TEDSTA ES PATENT OFFICE.

JOH T. AVERILL, OF ST. PAUL, MINNESOTA.

- IMPROVE M ENT I I N PROC E'S S'ES *FO R PR OD U-CIN G P U kP FROM WOO D.

Specification 'formingpart of Letters Patent No. 177,917, dated May 30, 1876; application filed I May 17, 1876.

of which pulp of superior strength and of light color can be produced from wood; and that; the following is a clear, full,.and exact des'criptionthereof.

Heretofore wood has been prepared for grinding by boiling in alkalineliquor orin water I under pressure, by which process the; fiber produced, though sufficiently long and. tough, has, nevertheless, acquired a dark COlOI'n My invention is "basedson lthe discovery that,

by boiling the wood in water at the ordinary atmospheric pressure a fiber is produced equal in length and toughness to that pro-,

duced by the above-described process, but of a lighter color, resembling the original color of the wood.

Long prior to the date of my invention amachine, commonly known as the Voelter machine, has been in use in this country by means of which wood is reduced to fiber by being ground upon a grindstone in presence of water, the pulp resulting from this process being manufactured into paper after being mixed with a certain percentage of pulp produced from rags, tow, jute, 860., so as to increase the strength of the paper. In this process the wood was applied to the grindstone in its natural state, or just as it comes from the tree.

Latelyviz., on the 21st of Apiil, 1874-a patent has been granted in this. country to- Voelter and Meyh for animproved process of making pulp from wood, in which the wood is described as being steamed in close vessels at a pressure of from forty-fiveto sixty pounds,

then bleached, and finally applied to a Voelter machine and reduced to pulp. The same patent also disclaims a process in which the wood is steamed under pressure in close vessels, and then applied to the Voelter machine without any bleaching, and upon that machine reduced to pulp,

The process claimed in this patent is an expensive one, but does-produce pulp of longer fiber than that produced in the old 'Voelter manner, and the wood, after being steamed and bleached, can be reduced to fiber with less expenditure of power than is required in proceeding according'to' the original Voelter, process.

The process disclaimed in the patent to Voelter and Meyh has also been'tried in this country with the result of increased lengthfof:

fiber as compared withthe originalVoelter .process,-and diminished power exerted in/the grinding; but the resulting fiber was of a dark-brown color, and useful only, in making inferior qualities of paper.

I desired toproducexwood fiber of the superior length and' with .the comparatively small expenditure of power obtained by the Voelter and Meyhprocess, but without the expense of bleaching the Wood, if'I employed the claimed process, and without the dark color which resulted from the use of the unclaimed process, and, after thought and experiment, succeeded by means of the process now to be described.

My process consists in subjecting the wood for a sufficient time to the action of boiling water in open vesselsthat is, vesselshaving a free communication with the air, or in subv ings, sawmill refuse, pieces cut from theedges of boards about an inch thick, pieces split 'from sawed bolts of wood, or pieces of board sawed to such lengths as are employed in Voelter machines, and put them into a wooden tub with a cover neither air nor steam tight; fill the tub with water, and then introduce steam through a pipe into the tubs; raise the water thus to about the boiling-point, and keep it boiling for thirty-six hours. The wood may be pine, fir, spruce, &c. After the boiling the wood is placed in the ordinary feedboxes of a Voelter machine and there ground, the result being a fiber as long or longer than that produced by the Voelter andMeyh process, and ot' a color-about that which is commonly termed Manilapapera color far superior to 2 lemon that which results from wood steamed under pressure and not bleached prior to being ground. I make from this pulp a fair wrapping-paper without any admixture. of other pulp, andwrapping-paper ofsuperior quality and color with a mixture of only fifteen per cent. of tow orjut'e pulp. This latter paper is as good and strong as paper having sixty per cent. of jute pulp and only forty per cent. of wood pulp made by the original Voe1ter process. 7

When poplar and other white woods, such as are now employed in making pulp for white paper by the original Voelter process, are treated by my new process, then the resultant pulp is of longer fiberthan before, while the color 'remains such that it can be used in making white paper without bleaching, and the power f required in grinding is diminished.

I am unable to explain exactly why my proplace in working out my process, and that it produces as good pulp, of as great a length of "fiber, and of asgood color, as the Voelter and Meyh process, and with as small expenditure ofpower in grinding, and'at much less expense, as bleaching is saved.

If wood of greater thickness than that'be; fore described be used the boiling must be longer continued. The wood, whether an inch or more thick, may be boiled in steam that is, kept in an atmosphere of steam at about the pressure of the atmosphere, without being actually immersed in water, as before described..

I do not desire to limit myself to the exact number of hours before mentioned as necessary to the boiling operation, since this must necessarily vary with the kind of wood employed, and the size of the pieces that are treated, the important'feature of my process being that the wood shall be boiled or steamed JNoQT. AVERILL.

Witnesses:

THOMAS C. GoNNo'LLY, JAS. H. PEIROE. 

